Thermally stable pcd with pcbn transition layer

ABSTRACT

The present disclosure relates to cutting tools incorporating polycrystalline diamond bodies used for subterranean drilling applications, and more particularly, to a thermally stable polycrystalline diamond body joined to a substrate to form a cutting element. The thermally stable polycrystalline diamond body may be binderless polycrystalline diamond or a non-metal catalyst polycrystalline diamond. A polycrystalline cubic boron nitride layer is also provided, bonded on one side to the polycrystalline diamond body and on the other side to the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/670,500 filed on Jul. 11, 2012, which is incorporated herein by reference in its entirety.

BACKGROUND

Ultra-hard materials are often used in cutting tools and rock drilling tools. Polycrystalline diamond material is one such ultra-hard material, and is known for its good wear resistance and hardness, making it a popular material choice for use in such industrial applications as cutting tools for machining and wear and cutting elements in subterranean mining and drilling.

To form polycrystalline diamond, diamond particles are sintered at high pressure and high temperature (HPHT sintering) to produce an ultra-hard polycrystalline structure. A catalyst material is added to the diamond particle mixture prior to sintering and/or infiltrates the diamond particle mixture during sintering in order to promote the intergrowth of the diamond crystals during HPHT sintering, to form the polycrystalline diamond (PCD) structure. Metals conventionally employed as the catalyst are selected from the group of solvent metal catalysts selected from Group VIII of the Periodic table, including cobalt, iron, and nickel, and combinations and alloys thereof. After HPHT sintering, the resulting PCD structure includes a network of interconnected diamond crystals bonded to each other, with the catalyst material occupying the interstitial spaces or pores between the bonded diamond crystals. The diamond particle mixture may be HPHT sintered in the presence of a substrate, to form a PCD body bonded to the substrate. The substrate may also act as a source of the metal catalyst that infiltrates into the diamond particle mixture during sintering.

A desired property of PCD bodies used for certain applications is improved thermal stability during wear or cutting operations. A problem known to exist with conventional PCD bodies is that they are vulnerable to thermal degradation when exposed to elevated temperatures. This vulnerability results from the differential that exists between the thermal expansion characteristics of the solvent metal catalyst material disposed interstitially within the PCD body and the thermal expansion characteristics of the intercrystalline bonded diamond. Such differential thermal expansion is known to start at temperatures as low as 400° C., and can induce thermal stresses that can be detrimental to the intercrystalline bonding of diamond and eventually result in the formation of cracks that can make the PCD structure vulnerable to failure. Further, the solvent metal catalyst is known to cause an undesired catalyzed phase transformation in diamond (converting it to carbon monoxide, carbon dioxide, or graphite) with increasing temperature, thereby limiting practical use of the PCD body to about 750° C.

Thermally stable PCD materials have been developed to improve performance at high temperatures. However, it can be difficult to form a bond between the thermally stable PCD material and a substrate, for attachment to a cutting tool.

SUMMARY

The present disclosure relates to cutting tools incorporating polycrystalline diamond bodies used for subterranean drilling applications, and more particularly, to a thermally stable polycrystalline diamond (PCD) body joined to a substrate to form a cutting element.

In an embodiment, a cutting element includes a thermally stable polycrystalline diamond body. The thermally stable PCD body may be binderless PCD or non-metal catalyst PCD, such as a carbonate PCD. A PCBN layer is also provided, bonded on one side to the PCD body and on the other side to a substrate. In an embodiment, a method is provided for joining a thermally stable polycrystalline diamond body to a substrate. The method includes forming a thermally stable PCD body, which may be binderless PCD or non-metal catalyst PCD. The method includes bonding the thermally stable polycrystalline diamond body to a polycrystalline cubic boron nitride body, and bonding the polycrystalline cubic boron nitride body to a carbide substrate.

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of thermally stable PCD materials are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components.

FIG. 1 illustrates a region of a thermally stable carbonate PCD material, in accordance with an embodiment.

FIG. 2 illustrates a region of a thermally stable binderless PCD material, in accordance with an embodiment.

FIG. 3 illustrates a cutting element incorporating a thermally stable PCD body, in accordance with an embodiment.

FIG. 4 illustrates a cutting element incorporating a thermally stable PCD body, in accordance with an embodiment.

FIG. 5 illustrates a cutting element incorporating a thermally stable PCD body, in accordance with an embodiment.

FIG. 6 illustrates example method(s) for bonding a thermally stable PCD body to a substrate, in accordance with one or more embodiments.

FIG. 7 illustrates example method(s) for bonding a thermally stable PCD body to a substrate, in accordance with one or more embodiments.

FIG. 8 illustrates an example device incorporating a cutting element, in accordance with an embodiment.

DETAILED DESCRIPTION

The present disclosure relates to cutting tools incorporating polycrystalline diamond material used for subterranean drilling applications, and more particularly, to a thermally stable polycrystalline diamond (PCD) body joined to a substrate to form a cutting element. In an embodiment, the thermally stable PCD material may be a non-metal catalyst PCD, or binderless PCD. The PCD body is bonded to a carbide substrate via a polycrystalline cubic boron nitride (PCBN) transition layer. The PCBN transition layer provides a bond to both the thermally stable PCD body and the carbide substrate.

The following disclosure is directed to various embodiments. The embodiments disclosed have broad application, and the discussion of any embodiment is meant only to be illustrative of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment or to the features of that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art would appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name only. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.

Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

For clarity, as used herein, the term “conventional PCD” refers to conventional polycrystalline diamond that has been formed with the use of a conventional metal catalyst during an HPHT sintering process, forming a microstructure of bonded diamond crystals with the metal catalyst material occupying the interstitial spaces or pores between the bonded diamond crystals.

“Non-metal catalyst PCD” refers to PCD material that has been formed with the use of a non-metal catalyst during an HPHT sintering process, forming a microstructure of bonded diamond crystals with the non-metal catalyst material occupying the interstitial spaces or pores between the bonded diamond crystals. Examples of non-metal catalysts include carbonates, sulfates (e.g., MgSO₄), hydroxides (e.g., Mg(OH)₂), and iron oxides (e.g., FeTiO₃). A carbonate catalyst may be any Group I or Group II carbonate, such as magnesium carbonate, calcium carbonate, lithium carbonate, or sodium carbonate, or combinations of carbonates. “Binderless PCD” refers to a polycrystalline diamond matrix that is formed without the use of a catalyst, such as by converting graphite directly to diamond at ultra-high pressure and temperatures. “Thermally stable PCD” as used herein means non-metal catalyst PCD or binderless PCD. In an embodiment, the thermally stable PCD is selected from the group consisting essentially of binderless PCD and non-metal catalyst PCD.

In an embodiment, the thermally stable PCD material is a non-metal catalyst PCD, such as a carbonate PCD. The non-metal catalyst is mixed with the diamond powder prior to sintering, and promotes the growth of diamond crystals during sintering. When a non-metal catalyst is used, the diamond remains stable in polycrystalline diamond form with increasing temperature up to 1200° C., rather than being converted to carbon dioxide, carbon monoxide or graphite. Thus the non-metal catalyst PCD is thermally stable.

In an embodiment, the non-metal catalyst PCD is made up of about 90-98% diamond (by volume), as well as the non-metal catalyst material, providing a total theoretical density of at least 98%, and in another embodiment at least 99%. A region of a carbonate PCD material 10 is schematically illustrated in FIG. 1. The carbonate PCD material 10 has a polycrystalline microstructure including multiple diamond grains or crystals 12 bonded to each other, with interstitial spaces or pores 14 between the diamond crystals 12.

This polycrystalline microstructure is formed by subjecting a diamond powder to an HPHT sintering process in the presence of a carbonate catalyst (or, in other embodiments, another non-metal catalyst). In one embodiment, the HPHT sintering process includes applying a pressure of about 70 kbar or greater, and a temperature of about 2,000 to 2,500° C. At this temperature and pressure, the non-metal catalyst material melts and infiltrates through the diamond powder mixture. The catalyst promotes the growth of diamond crystals during the HPHT sintering process, forming carbonate PCD. The result is a carbonate PCD material with the carbonate catalyst material 16 occupying the interstitial spaces 14 between the diamond crystals 12. In one embodiment, the diamond crystals 12 in the carbonate PCD material are about 1-50 microns in size, and provide a diamond volume content of at least 90%. In another embodiment the carbonate PCD has a diamond volume content of at least 95%. In another embodiment, the diamond crystals 12 are less than 1 micron in size.

In an embodiment, the thermally stable PCD material is a binderless PCD. Binderless PCD is formed without the use of a catalyst material. The resulting diamond material has a uniform intercrystalline diamond microstructure, without catalyst material interspersed between the diamond crystals. As a result, the binderless diamond body does not suffer from differential thermal expansion between diamond and catalyst. The binderless PCD is thermally stable.

A region of a binderless PCD material 20 is schematically illustrated in FIG. 2, according to an embodiment of the present disclosure. The binderless PCD 20 has a polycrystalline microstructure including multiple diamond grains or crystals 22 bonded to each other. As shown in FIG. 2, this material microstructure is substantially devoid of gaps or interstitial spaces between the diamond crystals 22. The diamond crystals 22 are bonded directly to each other. The binderless PCD 20 is substantially pure carbon, with a diamond volume fraction greater than 99%. There is substantially no binder phase or catalyst material between the diamond crystals 22.

This binderless PCD material 20 is described as “substantially” devoid of gaps and interstitial spaces, and “substantially” 100% diamond, in order to allow for the possibility of small imperfections and deviations within the binderless PCD 20 which may leave small gaps or spaces between some of the diamond crystals. In one embodiment the material microstructure of the binderless PCD material has a diamond volume content of at least 98%, and in another embodiment at least or about 99%, and in another embodiment at least or about 99.5%, and in another embodiment at least or about 99.8%, and in another embodiment at least or about 99.9%, and in another embodiment 100%. In one embodiment the binderless PCD material 20 has a fine diamond grain size, such as an average diamond grain size less than 1 micron, such as about 50 nm or less. Binderless PCD may also be referred to as “nano-PCD.” In other embodiments the binderless PCD material 20 has an average grain size of about 1-30 microns.

To form a binderless diamond material such as the material 20 shown in FIG. 2, carbon, in the form of graphite, buckeyballs or other carbon structures, is subjected to an ultra-high HPHT sintering process without a catalyst material. In one embodiment, this process includes HPHT sintering at ultra-high temperature and pressure, above that applied during conventional HPHT sintering to form PCD. In one embodiment, the pressure is between about 100-160 kbar, such as about 150 kbar, and the temperature is about 2200-2300° C. For example, when sintering graphite, the pressure may be about 150 kbar, or about 150-160 kbar. When sintering other types of carbon, such as buckeyballs or other complex carbon structures, the pressure may be about 110-120 kbar. For reference, conventional HPHT sintering to form PCD may be performed at about 50-60 kbar.

The method phase transforms the graphite (or other form of carbon) into polycrystalline diamond. That is, during the HPHT sintering process, the graphite converts into polycrystalline diamond, without the assistance of a catalyst material. Once the HPHT sintering is complete, the result is a thermally stable polycrystalline diamond matrix including bonded together diamond crystals substantially devoid of interstitial spaces, as discussed above.

In another embodiment, the thermally stable binderless diamond material 20 is formed by depositing layers in a chemical vapor deposition (CVD) process, to form a binderless PCD material with substantially 100% diamond volume content. The CVD process is performed by heating gas precursors in a reactive environment, which results in the precursors reacting or decomposing on the surface of a substrate, forming the desired deposit. This process results in growth of diamond crystals on the substrate.

The binderless PCD material 20 is inherently thermally stable, due to its uniform diamond content. The binderless PCD 20 has one phase, and thus there is no differential thermal expansion between different phases of the material. As a result, diamond bodies formed from this binderless PCD material 20 can exhibit high strength even at elevated temperatures, where conventional PCD suffers from thermal degradation due to the differential expansion of the diamond and catalyst phases.

In an embodiment, a thermally stable PCD body (such as binderless PCD or non-metal catalyst PCD) is attached to a substrate via a polycrystalline cubic boron nitride (PCBN) transition layer, as illustrated in FIG. 3. FIG. 3 shows a cutting element 30 including an ultra-hard body 32 bonded to a substrate 34. The ultra-hard body 32 includes a thermally stable PCD body 36 and a PCBN body or layer 38. The PCBN body 38 acts as a transition layer between the thermally stable PCD body 36 and the substrate 34.

The PCBN layer 38 facilitates the bond between the thermally stable PCD body 36 and the substrate 34. As noted above, according to embodiments of the disclosure, the thermally stable PCD body 36 is formed without a conventional catalyst metal, such as cobalt. By contrast, in forming conventional PCD, the metal solvent catalyst that is used to facilitate diamond growth during HPHT sintering also forms a bond between the substrate and the conventional PCD body. However, with the thermally stable PCD body 36, such a metal solvent catalyst is not available to form a bond between the thermally stable PCD body and the substrate.

Bonding a thermally stable PCD body directly to a substrate can present a challenge. Binderless PCD substantially lacks interstitial spaces between the bonded diamond crystals (see FIG. 2), and non-metal catalyst PCD includes non-metal catalyst occupying the spaces (see FIG. 1). Thus the thermally stable PCD body substantially lacks empty interstitial spaces available to be filled with a bonding material (such as a metal solvent catalyst) that flows between the substrate and the PCD body, as during conventional HPHT sintering. Moreover, brazing a PCD body to a substrate may cause graphitization of the diamond surface during brazing at high braze temperatures. Graphite does not form a strong bond between the substrate and the PCD body. Furthermore, attempting to sinter a non-metal catalyst diamond powder mixture directly onto a conventional substrate may result in infiltration of metals from the substrate into the diamond powder layer, displacing the non-metal catalyst. For example, when a carbonate catalyst is used, cobalt from the substrate may infiltrate into the diamond powder layer, as cobalt melts at a lower temperature than carbonate does. This infiltration can reduce the thermal stability of the PCD body.

According to an embodiment, a bond may be formed by providing a PCBN body between the thermally stable PCD body and the substrate. The PCBN layer acts as a transition layer that can be bonded to both the thermally stable PCD body and to the substrate. In an embodiment, the PCBN layer is brazed to the substrate. The braze material reacts with the PCBN material, forming boride and nitride layers along the PCBN grain surface. This results in a strong chemical bond between the PCBN layer and the substrate.

Referring to FIG. 3, the PCBN body 38 is provided to facilitate a bond between the thermally stable PCD body 36 and the substrate 34. In an embodiment, the PCBN layer 38 is provided as a cylindrical body or disc between the thermally stable PCD body 36 and the substrate 34. The thermally stable PCD body 36 includes a top or working surface 40 with a cutting edge 42. Opposite the working surface 40 is an interface 44 where the thermally stable PCD body 36 meets the PCBN layer 38. On the opposite side of the PCBN body is a second interface 46 with the substrate. The PCBN layer 38 has opposite top and bottom surfaces, the top surface meeting the thermally stable PCD body 36 at the interface 44, and the bottom surface meeting the substrate 34 at the second interface 46.

The PCBN layer may be metal bonded PCBN, ceramic bonded PCBN, or binderless PCBN (cubic boron nitride with trace amount of hexagonal boron nitride sintered directly from hexagonal boron nitride conversion). The PCBN may be formed by HPHT sintering, or by a CVD process that forms a coating of PCBN material on a surface of the thermally stable PCD.

The PCBN body may be combined with the thermally stable PCD body and the substrate in various ways. In an embodiment, the thermally stable PCD body and the PCBN body are formed by HPHT sintering, and the PCBN body is subsequently brazed to a substrate. The HPHT sintering may be done in one or two processes. In another embodiment, the PCBN body may be bonded to the substrate by HPHT sintering.

In one embodiment, the thermally stable PCD body and the PCBN body are sintered together in one HPHT sintering process. For example, diamond powder is mixed with a non-metal catalyst, and then placed next to CBN powder (with a suitable metal or ceramic binder) in a can. The can is then subjected to HPHT sintering conditions to form thermally stable PCD and PCBN, bonded together. During the HPHT sintering process, a bond is formed between the thermally stable PCD body and the PCBN body. In an embodiment, the PCBN is sintered with a ceramic binder (such as a titanium binder). The ceramic binder reacts with the CBN to form reaction bonding within the CBN layer, forming PCBN. Bonding also occurs at the interface between the CBN and the diamond layer. When the ultra-hard body is cooled, the PCBN body and the thermally stable PCD body are sintered and bonded together. In another embodiment, the PCBN is sintered with a metal binder, such as cobalt. During HPHT sintering, the cobalt binder melts and flows through the CBN layer, promoting the formation of PCBN. The cobalt may reach the interface with the diamond layer, and wet the surface of the diamond to form a bond between the diamond and PCBN. In an embodiment, binderless PCD and binderless PCBN may also be sintered and bonded together in one ultra-high pressure HPHT sintering process.

In one embodiment, the PCBN layer may also include PCD. In this case, the layer is formed by a mixture of diamond powder and CBN powder, and a binder material. During HPHT sintering, the CBN powder forms PCBN, and the diamond powder forms PCD, resulting in a mixed layer of both PCBN and PCD, bonded to the thermally stable PCD layer. The formation of PCBN from CBN powder by HPHT sintering is well documented in the art.

In an embodiment, the thermally stable PCD body and the PCBN body are sintered together in two separate HPHT sintering processes. The thermally stable PCD is formed in a first HPHT sintering process, forming either non-metal catalyst PCD or binderless PCD. Subsequently, the thermally stable PCD body is combined with CBN powder (and a suitable binder) and placed into a press. A second HPHT sintering process is then performed to convert the CBN into PCBN and to bond the PCBN to the thermally stable PCD. In an embodiment, the PCBN is sintered with a ceramic binder (such as a titanium-based binder). The second HPHT sintering process results in a PCBN layer bonded to the thermally stable PCD body. After the thermally stable PCD and the PCBN bodies have been formed and bonded together, the PCBN may then be brazed to a substrate to form a cutting element.

In an embodiment, the thermally stable PCD body, the PCBN body, and the substrate are sintered together in one HPHT sintering process. For example, diamond powder is mixed with a non-metal catalyst, and then placed next to CBN powder (with a suitable metal or ceramic binder), which is placed next to a substrate in a can. The can is then subjected to HPHT sintering conditions to form thermally stable PCD bonded to a PCBN layer bonded to a substrate. During HPHT sintering, cobalt may infiltrate from the substrate into the PCBN layer. The depth of infiltration of the cobalt can be less than the thickness of the PCBN layer, so that the cobalt does not reach the diamond layer. In an embodiment, the cobalt may be allowed to reach the diamond layer, and in one embodiment may even infiltrate partially into the diamond layer.

A cutting element 31 according to an embodiment is shown in FIG. 4. The cutting element 31 includes a thermally stable PCD body 36 bonded to a substrate 34 with a PCBN body 38 between them. In FIG. 4, the PCBN body 38 is bonded to the substrate 34 by a braze layer 48. The braze layer 48 may include an active braze material (such as titanium, silicon, or other carbide or oxide compounds) or an inactive braze material. Active and inactive braze materials are well known in the art.

The cutting elements shown in FIGS. 3 and 4 include an ultra-hard body that incorporates a thermally stable PCD body to form at least a portion of the cutting edge or working surface of the ultra-hard body. In one embodiment, the thermally stable PCD body forms at least a part of the working surface and/or the cutting edge of the ultra-hard body, such as at least 5% of the cutting edge (as measured by the circumference of the diamond body). For example, as described in more detail below with respect to FIG. 5, a thermally stable PCD body 36A may form a portion of the working surface and/or cutting edge of the ultra-hard body.

A cutting element 33 according to an embodiment is shown in FIG. 5. The cutting element 33 includes an ultra-hard body 32 bonded to a substrate 34. The ultra-hard body 32 includes one or more thermally stable PCD bodies 36, 36A bonded to a PCBN body 38. The thermally stable PCD bodies are partially (36A) or completely (36) surrounded by the PCBN body 38, and may or may not form a part of the cutting edge 42 of the ultra-hard body 32. The ultra-hard body 32 may be formed by pre-forming the thermally stable PCD bodies 36, 36A (such as by HPHT sintering), and then positioning them as desired in or within a CBN powder layer, and subjecting the combined body to an HPHT sintering process, to form PCBN and to bond the thermally stable PCD bodies 36, 36A to the PCBN body 38. This HPHT sintering process may be done in the presence of the substrate 34, or the ultra-hard body 32 may be bonded to the substrate 34 subsequently, such as by brazing.

The substrate 34 can be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof. Examples include carbides such as WC, W 2 C, TiC, VC. In one embodiment, the substrate is formed of cemented tungsten carbide.

As described above, the thermally stable PCD body and the PCBN body may be formed together during one HPHT sintering process, or the thermally stable PCD body may be formed in a first HPHT sintering process, and may be bonded to the PCBN body in a second HPHT sintering process. Other variations are also possible. For example, the thermally stable PCD body may be formed first (either by HPHT sintering, or CVD deposition of binderless PCD, described above), and the PCBN layer may then be formed on a surface of the thermally stable PCD body by a CVD process. In the CVD process, reactive gases form the cubic phase of boron nitride on a substrate and grow.

When the PCBN is formed by HPHT sintering, the HPHT sintering may be done in the presence of a substrate in order to bond the PCBN body to the substrate. The PCBN body may be sintered with either a ceramic binder or a metal binder, or a mix of them. When a mix of ceramic and metal binders are used, they may be uniformly distributed in the PCBN layer, or non-uniformly distributed, such as providing a higher concentration of the metal binder proximate the substrate, and a higher concentration of the ceramic binder proximate the PCD body. When a metal binder (such as cobalt) is used, it may infiltrate into the PCBN layer from the adjacent substrate. The cobalt flows through the PCBN layer and forms an integral bond between the substrate and the PCBN body. When the cobalt reaches the thermally stable PCD body, it is substantially or completely prevented from flowing into the PCD body due to the substantial absence of empty interstitial spaces within the thermally stable PCD body. In one embodiment, the cobalt flows along the interface between the PCBN layer and the thermally stable PCD body and forms a bond along the interface. When the cutting element is cooled, the cobalt is fixed into place, bonded along this interface surface between the PCBN body and the thermally stable PCD body.

A method of bonding a thermally stable PCD body to a carbide substrate is shown in FIG. 6, according to an embodiment. The method includes forming a thermally stable PCD body (102). This may include forming a non-metal catalyst PCD body (104) or forming a binderless PCD body (106). As discussed above, forming non-metal catalyst PCD (104) may include HPHT sintering diamond particles in the presence of a non-metal catalyst. Forming binderless PCD (106) may include subjecting carbon to an ultra-high HPHT sintering process without a catalyst material, or depositing layers of diamond in a chemical vapor deposition (CVD) process. In each case, one or more thermally stable PCD bodies may be formed, for incorporation into the cutting element (see, e.g., FIGS. 3-5).

The method also includes bonding the thermally stable PCD body to a PCBN body (108). In an embodiment, forming the thermally stable PCD body (102) is performed at the same time as bonding the PCD body to the PCBN body (108), such as in a single HPHT sintering process. For example, a mixture of diamond powder and non-metal catalyst may be combined with a CBN powder (and selected catalyst) and subjected to an HPHT sintering process. The HPHT sintering process creates a polycrystalline structure in each of the two bodies, and bonds them together. The thermally stable PCD body is formed adjacent to the PCBN body. As another example, in an embodiment, a mixture of diamond powder and non-metal catalyst is combined with a pre-sintered PCBN body, and subjected to an HPHT sintering process. The diamond powder is thus sintered on the surface of the PCBN body, forming a thermally stable PCD body bonded to the PCBN body.

In an embodiment, forming the thermally stable PCD body (102) is performed before bonding the thermally stable PCD body to the PCBN body (108). The thermally stable PCD body may be formed separately in a first operation, such as a first HPHT sintering process, or a first CVD process. The thermally stable PCD body is then bonded to a PCBN body in a separate process, such as a HPHT sintering process or a CVD process.

Referring again to FIG. 6, the method also includes bonding the PCBN body to a substrate (110). In one embodiment, this includes brazing the PCBN body to the substrate. Brazing is performed after the thermally stable PCD body has been bonded to the PCBN body.

In an embodiment, bonding the thermally stable PCD body to the PCBN body is performed at the same time as bonding the PCBN body to the substrate. For example, this may include HPHT sintering the PCBN body in the presence of a substrate. A thermally stable PCD body may be placed next to or surrounded by a layer of CBN powder, which is placed next to a substrate. The combination is subjected to an HPHT sintering process. The HPHT sintering process creates PCBN bonded to both the thermally stable PCD body and the substrate.

An example method is shown in FIG. 7. The method includes obtaining a thermally stable PCD body (114). The thermally stable PCD body may be non-metal catalyst PCD or binderless PCD. The method includes either HPHT sintering the thermally stable PCD body to a PCBN body (116) or HPHT sintering the thermally stable PCD body to a PCBN body in the presence of a substrate (118). In the former, the thermally stable PCD body is placed in a can with CBN particles, in the desired configuration for the ultra-hard body. That is, the PCD body may be positioned on one side of the CBN layer, or may be partially or fully surrounded by the CBN layer (see FIG. 5). The combination is then HPHT sintered, forming PCBN and forming a bond between the thermally stable PCD body and the PCBN body. Subsequently, the method includes brazing the PCBN body to a substrate (120).

In the latter method, the HPHT sintering process is conducted in the presence of a substrate (118). In this case, the HPHT sintering process results in two bonds—a first bond between the PCBN body and the thermally stable PCD body, and a second bond between the PCBN body and the substrate.

In another embodiment, the method includes obtaining a thermally stable PCD body (114), which may be non-metal catalyst PCD or binderless PCD. The method also includes sintering the thermally stable PCD body to a conventional PCD body. The method further includes either HPHT sintering the conventional PCD body to a PCBN body (116) or HPHT sintering the conventional PCD body to a PCBN body (116) in the presence of a substrate (118). Subsequently, the method includes brazing the PCBN body to a substrate (120).

The ultra-hard bodies shown in FIGS. 3-5 are formed as cutting elements for incorporation into a cutting tool. FIG. 8 shows a drag bit 50 incorporating a cutting element including a thermally stable PCD body bonded to a substrate by a PCBN layer. The drag bit 50 may include several cutting elements 30 that are each attached to blades 52 that extend along the drag bit. The drag bit may be used for high-temperature rock drilling operations. In other embodiments, other types of drilling or cutting tools incorporate cutting elements that have a thermally stable PCD body forming at least a portion of the cutting edge of the cutting element, such as, for example, rotary or roller cone drilling bits, or percussion or hammer drill bits. In one embodiment, the cutting element is a shear cutter.

While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments and modifications can be devised which do not materially depart from the scope of the present disclosure. Such embodiments and modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this disclosure. Accordingly, all such modifications are without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. It is the express intention of the applicant not to invoke 35 U.S.C. 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘mean for’ together with an associated function. 

What is claimed is:
 1. A cutting element comprising: at least one thermally stable polycrystalline diamond body comprising a material microstructure comprising a plurality of bonded-together diamond crystals, wherein the thermally stable polycrystalline diamond body is selected from the group of bodies consisting essentially of binderless polycrystalline diamond bodies and non-metal catalyst polycrystalline diamond bodies; a layer comprising polycrystalline cubic boron nitride, the layer being bonded to the thermally stable polycrystalline diamond body and having an interface surface; and a substrate, wherein the interface surface of the polycrystalline cubic boron nitride layer is bonded to the substrate.
 2. The cutting element of claim 1, wherein the at least one thermally stable polycrystalline diamond body comprises the non-metal catalyst polycrystalline diamond body, wherein the non-metal catalyst material is selected from the group consisting essentially of carbonates, sulfates, hydroxides, and iron oxides, and wherein the material microstructure further comprises interstitial regions between the diamond crystals, and the non-metal catalyst material occupying the interstitial regions.
 3. The cutting element of claim 1, wherein the at least one thermally stable polycrystalline diamond body comprises binderless polycrystalline diamond.
 4. The cutting element of claim 3, wherein the binderless polycrystalline diamond comprises a diamond volume content of at least 98%.
 5. The cutting element of claim 1, wherein the polycrystalline cubic boron nitride layer is bonded to the substrate by a braze layer.
 6. The cutting element of claim 1, wherein the polycrystalline cubic boron nitride layer is bonded to the substrate by high pressure high temperature sintering.
 7. The cutting element of claim 1, wherein the polycrystalline cubic boron nitride layer includes a mixture of polycrystalline cubic boron nitride and polycrystalline diamond.
 8. The cutting element of claim 1, wherein the at least one thermally stable polycrystalline diamond body comprises a plurality of bodies, at least one of which is surrounded by the polycrystalline cubic boron nitride layer.
 9. The cutting element of claim 1, wherein the at least one thermally stable polycrystalline diamond body comprises a top surface, a cutting edge meeting the top surface, and a bottom surface opposite the top surface, and wherein the bottom surface of the thermally stable polycrystalline diamond body is bonded to the polycrystalline cubic boron nitride layer.
 10. The cutting element of claim 1, wherein the polycrystalline cubic boron nitride layer comprises a ceramic binder or a metal binder.
 11. A shear cutter, comprising: a thermally stable polycrystalline diamond body comprising: an interface surface; a top surface opposite the interface surface; a cutting edge at the top surface; and a material microstructure comprising a plurality of bonded-together diamond crystals; a polycrystalline cubic boron nitride transition layer having opposite first and second surfaces; a first bond between the first surface of the polycrystalline cubic boron nitride transition layer and the interface surface of the polycrystalline diamond body; a substrate; and a second bond between the second surface of the polycrystalline cubic boron nitride transition layer and the substrate, wherein the thermally stable polycrystalline diamond body is selected from the group of bodies consisting essentially of binderless polycrystalline diamond bodies and non-metal catalyst polycrystalline diamond bodies.
 12. The shear cutter of claim 11, wherein the first bond comprises a ceramic binder.
 13. The shear cutter of claim 11, wherein the second bond comprises a braze.
 14. The shear cutter of claim 11, wherein the second bond is formed by high pressure high temperature sintering.
 15. A method for joining a thermally stable polycrystalline diamond body to a substrate, comprising: bonding a thermally stable polycrystalline diamond body to a polycrystalline cubic boron nitride body; and bonding the polycrystalline cubic boron nitride body to a substrate.
 16. The method of claim 15, further comprising forming the thermally stable polycrystalline diamond body by sintering diamond particles and a non-metal catalyst at high temperature and high pressure to form a non-metal catalyst thermally stable polycrystalline diamond.
 17. The method of claim 15, further comprising forming the thermally stable polycrystalline diamond body by subjecting carbon to an ultra-high pressure, high temperature sintering process without a catalyst material, to form binderless thermally stable polycrystalline diamond.
 18. The method of claim 15, wherein bonding the thermally stable polycrystalline diamond body to the polycrystalline cubic boron nitride body comprises sintering the thermally stable polycrystalline diamond body in contact with cubic boron nitride particles at high temperature and high pressure.
 19. The method of claim 15, wherein bonding the polycrystalline cubic boron nitride body to the carbide substrate comprises brazing.
 20. The method of claim 15, wherein bonding the polycrystalline cubic boron nitride body to the carbide substrate comprises sintering cubic boron nitride particles in contact with a substrate at high temperature and high pressure. 